{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "bdd0ec06",
   "metadata": {},
   "source": [
    "# 函数\n",
    "\n",
    "## 1.函数的定义\n",
    "> 1.数字：f(x)=ax+b  \n",
    "> 2.python: def fib(x)  \n",
    "> 3.编程思维 vs 数学思维  \n",
    "\n",
    ">> 1.函数可以被定义名称,定义的关键字<font style='color:red'>**def**</font>  \n",
    ">> 2.数学思维是写在同一行（定义函数 和 运算公式），面向对象编程中函数写多行，定义函数为单独一行  \n",
    ">> 3.数学函数一般没有注释，而编程过程中，一般需要对函数进行注释描述（docstring）  \n",
    ">> 4.数学中：ax+b是计算公式，而编程中，我们将函数的内容成为**函数体**，函数体要有一定的**缩进**  \n",
    ">> 5.数学函数执行，将参数代入公式，编程中函数执行，将参数代入函数体  \n",
    "\n",
    "## 2.关于函数的更多定义\n",
    ">1.函数的参数  \n",
    ">>1.形式参数  \n",
    ">>2.实际参数  \n",
    ">>3.默认参数  \n",
    ">>4.位置参数  \n",
    ">>5.关键字参数  \n",
    "\n",
    "## 函数的定义\n",
    "> 1.定义函数\n",
    "\n",
    "```\n",
    " 1.def:定义函数的关键字  \n",
    " 2.flb：函数名  \n",
    " 3.(n)：定义函数的参数  \n",
    "\"\"\"  \"\"\"：文档描述 : 与使用者进行 交互的唯一途径  \n",
    " 4.代码块：  \n",
    "     a, b = 0, 1  \n",
    "     while a < n:  \n",
    "        print(a, end=' ')  \n",
    "         a, b = b, a+b  \n",
    "     print()  \n",
    "```"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "9361b71a",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 斐波那切数列：eg: 0 1 1 2 3 5 8 13 34....\n",
    "def fib(x):\n",
    "    \"\"\"列出指定x以内的斐波那切数列\"\"\"\n",
    "    a,b = 0,1\n",
    "    while a < x :\n",
    "        print(a,end='')\n",
    "        a,b = b, a+b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "df22818a",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "01123581321345589"
     ]
    }
   ],
   "source": [
    "fib(100)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "64fd1b8a",
   "metadata": {
    "scrolled": false
   },
   "outputs": [],
   "source": [
    "# 实践： 请大家写一个函数，这个函数可以打印“你好，xxx同学”\n",
    "def hello(name):\n",
    "    \"\"\"显示问候语\"\"\"\n",
    "    print(\"你好，%s同学\"%(name))"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c5fd2f64",
   "metadata": {},
   "source": [
    ">2.调用函数/使用函数  \n",
    ">>1.函数名(参数)  \n",
    ">>2.参数可以不存在"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "id": "4b691f32",
   "metadata": {
    "scrolled": true
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "你好，石同学\n"
     ]
    }
   ],
   "source": [
    "hello(\"石\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "22a11610",
   "metadata": {},
   "outputs": [],
   "source": [
    "def hello():\n",
    "    \"\"\"显示问候语\"\"\"\n",
    "    print(\"hello world\")\n",
    "    "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "fdc132ca",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Help on function hello in module __main__:\n",
      "\n",
      "hello()\n",
      "    显示问候语\n",
      "\n"
     ]
    }
   ],
   "source": [
    "help(hello)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "id": "94dd07a7",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hello world\n"
     ]
    }
   ],
   "source": [
    "hello()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "id": "84165b77",
   "metadata": {},
   "outputs": [],
   "source": [
    "#回顾与思考\n",
    "import time"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "id": "da350169",
   "metadata": {},
   "outputs": [],
   "source": [
    "#sleep()需要给定一个时间(int)参数\n",
    "time.sleep(3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "id": "3caed8a2",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "time.struct_time(tm_year=2021, tm_mon=12, tm_mday=21, tm_hour=11, tm_min=23, tm_sec=56, tm_wday=1, tm_yday=355, tm_isdst=0)"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# localtime()不需要给定函数\n",
    "time.localtime()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "id": "4b52caca",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Help on built-in function localtime in module time:\n",
      "\n",
      "localtime(...)\n",
      "    localtime([seconds]) -> (tm_year,tm_mon,tm_mday,tm_hour,tm_min,\n",
      "                              tm_sec,tm_wday,tm_yday,tm_isdst)\n",
      "    \n",
      "    Convert seconds since the Epoch to a time tuple expressing local time.\n",
      "    When 'seconds' is not passed in, convert the current time instead.\n",
      "\n"
     ]
    }
   ],
   "source": [
    "help(time.localtime)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "f06dd07d",
   "metadata": {},
   "source": [
    ">3.函数的优势  \n",
    ">>1.可以重复使用相同的功能，避免重复造轮子  \n",
    ">>2.使用者可以不了解函数本身，只需要清楚如何使用即可  \n",
    ">>3.使用/调用方便，只需要清楚传递的 函数名及参数  \n",
    "\n",
    "\n",
    "## 3.函数的参数\n",
    "> 1.形式函数(形参)  \n",
    ">>1.在**定义**函数的时候定义的参数  \n",
    ">>2.形参不占用内存\n",
    "\n",
    "> 2.实际参数（实参）\n",
    ">>1.在**调用**函数的时候传递参数  \n",
    ">>2.调用函数时，形参分配空间，传递实参，执行参数内容\n",
    "\n",
    "* 课本函数实践案例\n",
    "```\n",
    "def search4vowels(word):\n",
    "    \"\"\"显示文本中出现的元音字母有哪些\"\"\"\n",
    "    vowels = set(\"aeiou\")\n",
    "    word = set(word)\n",
    "    print(vowels & word)\n",
    "```\n",
    ">形式参数： word  \n",
    ">实际参数：\"fbheduigpewjiewmcfkdlaepw\"\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "id": "5342198b",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 课本函数实践案例\n",
    "def search4vowels(word):\n",
    "    \"\"\"\n",
    "    显示文本中出现的元音字母有哪些\n",
    "    \n",
    "    word是文本信息，请输入正确的文本给word\n",
    "    \"\"\"\n",
    "    vowels = set(\"aeiou\")\n",
    "    word = set(word)\n",
    "    print(vowels & word)\n",
    "    "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "id": "7c91008d",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Help on function search4vowels in module __main__:\n",
      "\n",
      "search4vowels(word)\n",
      "    显示文本中出现的元音字母有哪些\n",
      "    \n",
      "    word是文本信息，请输入正确的文本给word\n",
      "\n"
     ]
    }
   ],
   "source": [
    "help(search4vowels)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "id": "ce0d47ee",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'i', 'o', 'u', 'e', 'a'}\n"
     ]
    }
   ],
   "source": [
    "seach4vowels(\"abcdefghijklnmopqrstuvwxyz\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "9d591a48",
   "metadata": {},
   "source": [
    "* 在多个参数\n",
    "> 1.位置参数\n",
    ">>1.1在形式参数的定义中，有一定的先后顺序  \n",
    ">>1.2在调用函数时，要考虑形参的先后顺序  \n",
    ">>1.3调用函数时，不仅要考虑参数位置，还需要考虑形式参数的个数  \n",
    "\n",
    "> 2.关键字参数  \n",
    ">>2.1在调用函数时，关键字参数可以不考虑形式参数的位置  \n",
    "\n",
    "> 3.调用参数时  \n",
    ">>3.1调用函数时，可以省略传递的参数信息  \n",
    ">>3.2调用函数时，如果给默认参数赋值，会替换默认参数的结果"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "87fc6656",
   "metadata": {},
   "outputs": [],
   "source": [
    "def describe_pet(pet_name,animal_type):\n",
    "    \"\"\"显示宠物信息\"\"\"\n",
    "    print(\"\\nI have a \" + animal_type + \".\")\n",
    "    print(\"My \" + animal_type + \"'s name is \"+pet_name.title() + \".\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "37dc75ae",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have a dog.\n",
      "My dog's name is 豆豆.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(\"豆豆\",\"dog\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "44ff4f8a",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have a 豆豆.\n",
      "My 豆豆's name is Dog.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(\"dog\",\"豆豆\")\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "f3bbb311",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have a cat.\n",
      "My cat's name is 纽扣.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(animal_type=\"cat\",pet_name=\"纽扣\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "755b8360",
   "metadata": {},
   "outputs": [],
   "source": [
    "## 默认参数\n",
    "def describe_pet(pet_name,animal_type=\"dog\"):\n",
    "    \"\"\"显示宠物信息\"\"\"\n",
    "    print(\"\\nI have a \" + animal_type + \".\")\n",
    "    print(\"My \" + animal_type + \"'s name is \"+pet_name.title() + \".\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "efec61d1",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have a cat.\n",
      "My cat's name is 豆豆.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(\"豆豆\",\"cat\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "f8156b8b",
   "metadata": {},
   "source": [
    "* 参数注意事项实践 \n",
    ">1.位置参数和关键字参数同时使用（调用函数）  \n",
    ">>1.1positional argument follows keyword argument（关键字参数均应该放在位置参数之后）  \n",
    ">>1.2只要满足1的条件，剩余的关键字参数（多个）不考虑先后顺序\n",
    "\n",
    ">2.非默认参数和默认参数同时使用（定义函数）  \n",
    ">>2.1non-default argument follows default argument（默认参数均应该放在非默认参数之后）  \n",
    ">>2.2只要满足1的条件，剩余的默认参数（多个）不考虑先后顺序"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "753862a5",
   "metadata": {},
   "outputs": [],
   "source": [
    "def test(x,y,z):\n",
    "    \"\"\"打印x,y,z的结果\"\"\"\n",
    "    print(x)\n",
    "    print(y)\n",
    "    print(z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "f0342c6d",
   "metadata": {},
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "positional argument follows keyword argument (<ipython-input-2-489fdb94d38c>, line 2)",
     "output_type": "error",
     "traceback": [
      "\u001b[1;36m  File \u001b[1;32m\"<ipython-input-2-489fdb94d38c>\"\u001b[1;36m, line \u001b[1;32m2\u001b[0m\n\u001b[1;33m    test(5,y=3,2)\u001b[0m\n\u001b[1;37m               ^\u001b[0m\n\u001b[1;31mSyntaxError\u001b[0m\u001b[1;31m:\u001b[0m positional argument follows keyword argument\n"
     ]
    }
   ],
   "source": [
    "# 实践1：\n",
    "test(5,y=3,2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "ddd7b460",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "5\n",
      "3\n",
      "2\n"
     ]
    }
   ],
   "source": [
    "# 实践2：\n",
    "test(5,3,z = 2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "6a53ff6a",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "5\n",
      "2\n",
      "3\n"
     ]
    }
   ],
   "source": [
    "# 实践3：\n",
    "test(5,z=3,y=2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "27dbe0f9",
   "metadata": {},
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "non-default argument follows default argument (<ipython-input-5-eac1f1ed18cb>, line 2)",
     "output_type": "error",
     "traceback": [
      "\u001b[1;36m  File \u001b[1;32m\"<ipython-input-5-eac1f1ed18cb>\"\u001b[1;36m, line \u001b[1;32m2\u001b[0m\n\u001b[1;33m    def test(x,y=1,z):\u001b[0m\n\u001b[1;37m             ^\u001b[0m\n\u001b[1;31mSyntaxError\u001b[0m\u001b[1;31m:\u001b[0m non-default argument follows default argument\n"
     ]
    }
   ],
   "source": [
    "# 测试2：\n",
    "def test(x,y=1,z):\n",
    "    \"\"\"打印x,y,z的结果\"\"\"\n",
    "    print(x)\n",
    "    print(y)\n",
    "    print(z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "20a85b99",
   "metadata": {},
   "outputs": [],
   "source": [
    "def test(x,z,y=1):\n",
    "    \"\"\"打印x,y,z的结果\"\"\"\n",
    "    print(x)\n",
    "    print(y)\n",
    "    print(z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "7af799b1",
   "metadata": {},
   "outputs": [],
   "source": []
  }
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